antibiotics and antibacterials: what's the difference?

'Antibiotic' usually refers to medications which treat bacterial infections by killing the bacteria involved. 'Anti-bacterial' usually refers to cleaning products which kill bacteria on surfaces before they get into the body. Penicillin and its variants are 'antibiotics' and are taken into the body orally or by injection. They work by targeting bacterial infections in the body itself and they can be specific to certain types of bacteria. It's worth noting that they CANNOT deal with viral infections (like flu or the common cold) but they can deal with bacterial infections which may often be associated with the viral infection. Strictly speaking, the word 'anti-bacterial' could be applied to these medications (because that is their action) but normally is is used for hand wash and surface cleaning products whose action is a chemical one.

An antibiotic is a medicine that assists your immune system to fight off an infection of bacteria in your body. Something that is antibacterial kills bacteria on contact, like a cleanser that will kill e coli bacteria that dripped from some raw chicken onto your kitchen counter. They are not the same, because if you have an infection, drinking some antibacterial cleanser will not make your infection go away, and grinding up an antibiotic pill and sprinkling it on your counter will not disinfect your counter.